Fe(II)-based reductive dechlorination of tetrachloroethylene in soils treated by degradative solidification/stabilization /
Remediation of soils contaminated with chlorinated organics and mixtures of chlorinated organics and metals is a major environmental problem. Degradative solidification/stabilization (DS/S) is a potential new technology for such applications. DS/S is a modification of conventional S/S processes th...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731990131&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Remediation of soils contaminated with chlorinated organics and mixtures of chlorinated organics and metals is a major environmental problem. Degradative solidification/stabilization (DS/S) is a potential new technology for such applications. DS/S is a modification of conventional S/S processes that promotes degradation of organic contaminants while containing them as well as containing inorganic contaminants. Experiments were conducted to identify combinations of reagents and reaction conditions that are appropriate for use in DS/S of chlorinated organics and to demonstrate the feasibility of using one combination in treating contaminated soils. Tetrachloroethylene was chosen as a model chlorinated compound for this study. First, screening experiments were conducted to evaluate a variety of combinations of reagents that could be used in DS/S of chlorinated organics. The screening experiments identified the degradation system consisting of Portland cement and Fe(II) as a promising one. Second, degradation reactions of PCE in Fe(II)/cement systems were further characterized using batch slurry reactors. Cement has been found to catalyze or participate in the PCE degradation reactions over the pH range investigated (10.6-13.8). The degradation kinetics of PCE in Fe(II)/cement systems can generally be described by a pseudo first-order rate law. The PCE degradation rate was greatest at pH values near 12.1 with a half-life of 4.1 days when [Fe(II)] was 39.2 mM. Production of chlorinated intermediates was minimal in Fe(II)/cement systems, and acetylene appeared to be a predominant final product. Addition of Fe(III) to Fe(II)/cement systems increased PCE degradation rates by factors of ~ 2 to 3, suggesting Fe(II)-Fe(III) (hydr)oxides might have been reactive reagents. Three hypotheses for the reaction mechanisms are discussed. Finally, the effectiveness of the Fe(II)/cement system in treating a PCE-contaminated soil was demonstrated. Half-lives of PCE in the solidified matrices ranged from 13 to 335 days, which are well suited to time spans allowable for remediation of contaminated soils in situ. TCE was the only chlorinated byproduct observed in the soil experiments and its presence was transitory with the amount being less than 7% of the initial amount of PCE on a molar basis. |
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| Item Description: | Vita. "Major Subject: Civil Engineering". |
| Physical Description: | xii, 165 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 123-133). |